
104
through an inductance L is inversely proportional to L. And in Sec.
4.6 we noted that the inductance of an ideal inductor of the type we
are considering is directly proportional to the permeability, μ of the
core,
and to the square of N, the number of turns. The iron core of a
transformer normally has a μ running into thousands, and Ν is
usually considerable, so the inductance is likely to be very large and
the current therefore quite small. That is why AB is drawn so short in
Fig. 7.6Z?. AB is called the magnetising current because its purpose is
to generate sufficient alternating magnetic flux in the core to induce
an
e.m.f.
in the primar ...